The present invention relates to the utilization of moist biomass as an energy source, in particular of grain and, above all, corn.
Dry grain is used as an energy source in isolated cases, but doing so raises ethical concerns, because the grain could theoretically be used as a source of food for the human population. Grain that is harvested while moist, and that is traditionally used only as cattle feed, does not raise these ethical concerns. Corn, for instance, which is cultivated for use as livestock feed in many areas in Europe, often requires a longer vegetation time to mature than the climate allows. It must therefore be harvested in the moist state, when its quality makes it unsuitable for use as a food source for the human population.
One problem associated with the use of biomass—regardless of the type—as an energy source is its water content. A high water content reduces the storability of the biomass, results in high hauling costs, reduces the energy yield of combustion, and lowers the exhaust quality. Drying the biomass in open spaces requires a great deal of time and large spaces, and drying the biomass by heating it often consumes more energy than may be produced via the combustion of the dry biomass.
DE 10 2004 003 011 A1 makes known a generic device that includes a dehydration device for mechanically pre-dehydrating the biomass, and a drying step for post-dehydrating the pre-dehydrated biomass via the addition of heat. In this case as well, the use of primary energy that is required to make the biomass usable for further processing so that it may used directly or indirectly as an energy carrier is crucially dependent on the extent pre-dehydration that is attainable using the mechanical dehydration device, and on the efficiency of the drying step.